Vfr or CyaB promote the expression of the pore-forming toxin exlBA operon in Pseudomonas aeruginosa ATCC 9027 without increasing its virulence in mice

Microbiology ◽  
2021 ◽  
Vol 167 (8) ◽  
Author(s):  
Selene García-Reyes ◽  
Dina A. Moustafa ◽  
Ina Attrée ◽  
Joanna B. Goldberg ◽  
Sara E. Quiroz-Morales ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Mouse Models ◽  
Type Species ◽  
Transcriptional Control ◽  
Galleria Mellonella ◽  
Health Hazard ◽  
Transcriptional Regulator ◽  
Strain Atcc ◽  
Content Type ◽  
Link Type

Pseudomonas aeruginosa is a wide-spread γ-proteobacterium that produces the biosurfactant rhamnolipid that has a great commercial value due to excellent properties of low toxicity and high biodegradability. However, this bacterium is an opportunist pathogen that constitutes an important health hazard due to its production of virulence-associated traits and its high antibiotic resistance. Thus, it is highly desirable to have a non-virulent P. aeruginosa strain for rhamnolipid production. It has been reported that strain ATCC 9027 is avirulent in mouse models of infection, and it is still able to produce rhamnolipid. Thus, it has been proposed to be suitable for it industrial production, since it encodes a defective LasR quorum sensing (QS) transcriptional regulator that is the head of this regulatory network. However, the restoration of virulence factor production by overexpression of rhlR (the gene encoding a QS-transcriptional regulator which is under the transcriptional control of LasR) is not sufficient to restore its virulence in mice. It is desirable to obtain a deeper understanding of ATCC 9027 attenuated-virulence phenotype and to assess the safety of this strain to be used at an industrial scale. In this work we determined whether increasing the expression of the pore-forming toxin encoded by the exlBA operon in strain ATCC 9027 had an impact on its virulence using Galleria mellonella and mouse models of infections. We increased the expression of the exlBA operon by overexpressing from a plasmid its transcriptional activator Vfr or of the Vfr ligand cyclic AMP produced by CyaB. We found that in G. mellonella ATCC 9027/pUCP24-vfr and ATCC 9027/pUCP24-cyaB gained a virulent phenotype, but these strains remained avirulent in murine models of P. aeruginosa infection. These results reinforce the possibility of using ATCC 9027 for industrial biosurfactants production.

scholarly journals Delivery of antibacterial silver nanoclusters to Pseudomonas aeruginosa using species-specific DNA aptamers

2020 ◽  
Vol 69 (4) ◽  
pp. 640-652 ◽  
Author(s):  
Jennifer Soundy ◽  
Darren Day
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Antimicrobial Activity ◽  
Type Species ◽  
Galleria Mellonella ◽  
Host Cells ◽  
Silver Nanoclusters ◽  
Bacterial Cells ◽  
Content Type ◽  
Link Type

Introduction. The use of silver as an antimicrobial therapeutic is limited by its toxicity to host cells compared with that required to kill bacterial pathogens. Aim. To use aptamer targeting of DNA scaffolded silver nanoclusters as an antimicrobial agent for treating Pseudomonas aeruginosa infections. Methodology. Antimicrobial activity was assessed in planktonic cultures and in vivo using an invertebrate model of infection. Results. The aptamer conjugates that we call aptabiotics have potent antimicrobial activity. Targeted silver nanoclusters were more effective at killing P. aeruginosa than the equivalent quantity of untargeted silver nanoclusters. The aptabiotics have an IC50 of 1.3–2.6 µM against planktonically grown bacteria. Propidium iodide staining showed that they rapidly depolarize bacterial cells to kill approximately 50 % of the population within 10 min following treatment. In vivo testing in the Galleria mellonella model of infection prolonged survival from an otherwise lethal infection. Conclusion. Using P. aeruginosa as a model, we show that targeting of DNA-scaffolded silver nanoclusters with an aptamer has effective fast-acting antimicrobial activity in vitro and in an in vivo animal model.

scholarly journals Reclassification of Bacteriovorax marinus as Halobacteriovorax marinus gen. nov., comb. nov. and Bacteriovorax litoralis as Halobacteriovorax litoralis comb. nov.; description of Halobacteriovoraceae fam. nov. in the class Deltaproteobacteria

2015 ◽  
Vol 65 (Pt_2) ◽  
pp. 593-597 ◽  
Author(s):  
Susan F. Koval ◽  
Henry N. Williams ◽  
O. Colin Stine
Keyword(s):  
Type Strain ◽  
Type Species ◽  
Taxonomic Status ◽  
Strain Atcc ◽  
Content Type ◽  
Link Type ◽  
As Species ◽  
Previous Proposal

The taxonomic status of saltwater Bdellovibrio -like prokaryotic predators has been revised to assign species to Halobacteriovorax gen. nov. A reclassification of Bacteriovorax marinus as Halobacteriovorax marinus comb. nov. (type strain ATCC BAA-682T = DSM 15412T) and Bacteriovorax litoralis as Halobacteriovorax litoralis comb. nov. (type strain ATCC BAA-684T = DSM 15409T) is proposed. This revision is necessary because a previous proposal to retain saltwater isolates as species of Bacteriovorax and reclassify Bacteriovorax stolpii as Bacteriolyticum stolpii was not approved. The type species of a genus cannot be reassigned to another genus. Bacteriovorax stolpii is thus retained as the type species of Bacteriovorax and Halobacteriovorax marinus is the type species of Halobacteriovorax and of Halobacteriovoraceae fam. nov.

scholarly journals AzeR, a transcriptional regulator that responds to azelaic acid in Pseudomonas nitroreducens

Microbiology ◽  
2020 ◽  
Vol 166 (1) ◽  
pp. 73-84 ◽  
Author(s):  
Cristina Bez ◽  
Sree Gowrinadh Javvadi ◽  
Iris Bertani ◽  
Giulia Devescovi ◽  
Corrado Guarnaccia ◽  
...  
Keyword(s):  
Azelaic Acid ◽  
Type Species ◽  
Isocitrate Lyase ◽  
Model Organism ◽  
Transcriptional Regulator ◽  
Sole Source ◽  
Bacterial Degradation ◽  
Content Type ◽  
Link Type ◽  
Pseudomonas Nitroreducens

Azelaic acid is a dicarboxylic acid that has recently been shown to play a role in plant-bacteria signalling and also occurs naturally in several cereals. Several bacteria have been reported to be able to utilize azelaic acid as a unique source of carbon and energy, including Pseudomonas nitroreducens . In this study, we utilize P. nitroreducens as a model organism to study bacterial degradation of and response to azelaic acid. We report genetic evidence of azelaic acid degradation and the identification of a transcriptional regulator that responds to azelaic acid in P. nitroreducens DSM 9128. Three mutants possessing transposons in genes of an acyl-CoA ligase, an acyl-CoA dehydrogenase and an isocitrate lyase display a deficient ability in growing in azelaic acid. Studies on transcriptional regulation of these genes resulted in the identification of an IclR family repressor that we designated as AzeR, which specifically responds to azelaic acid. A bioinformatics survey reveals that AzeR is confined to a few proteobacterial genera that are likely to be able to degrade and utilize azelaic acid as the sole source of carbon and energy.

scholarly journals Mutations in the two component regulator systems PmrAB and PhoPQ give rise to increased colistin resistance in Citrobacter and Enterobacter spp.

2020 ◽  
Vol 69 (4) ◽  
pp. 521-529 ◽  
Author(s):  
Matthew E. Wand ◽  
J. Mark Sutton
Keyword(s):  
Growth Rate ◽  
Type Species ◽  
Galleria Mellonella ◽  
Strain Differences ◽  
Fold Increase ◽  
Colistin Resistance ◽  
Content Type ◽  
Link Type ◽  
Carbapenem Resistant ◽  
Individual Strain

Introduction. Colistin is a last resort antibiotic for treating infections caused by carbapenem-resistant isolates. Mechanisms of resistance to colistin have been widely described in Klebsiella pneumoniae and Escherichia coli but have yet to be characterized in Citrobacter and Enterobacter species. Aim. To identify the causative mutations leading to generation of colistin resistance in Citrobacter and Enterobacter spp. Methodology. Colistin resistance was generated by culturing in increasing concentrations of colistin or by direct culture in a lethal (above MIC) concentration. Whole-genome sequencing was used to identify mutations. Fitness of resistant strains was determined by changes in growth rate, and virulence in Galleria mellonella. Results. We were able to generate colistin resistance upon exposure to sub-MIC levels of colistin, in several but not all strains of Citrobacter and Enterobacter resulting in a 16-fold increase in colistin MIC values for both species. The same individual strains also developed resistance to colistin after a single exposure at 10× MIC, with a similar increase in MIC. Genetic analysis revealed that this increased resistance was attributed to mutations in PmrB for Citrobacter and PhoP in Enterobacter , although we were not able to identify causative mutations in all strains. Colistin-resistant mutants showed little difference in growth rate, and virulence in G. mellonella, although there were strain-to-strain differences. Conclusions. Stable colistin resistance may be acquired with no loss of fitness in these species. However, only select strains were able to adapt suggesting that acquisition of colistin resistance is dependent upon individual strain characteristics.

scholarly journals Characterization of the φCTX-like Pseudomonas aeruginosa phage Dobby isolated from the kidney stone microbiota

2019 ◽  
Vol 1 (1) ◽  
Author(s):  
Genevieve Johnson ◽  
Alan J. Wolfe ◽  
Catherine Putonti
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Urinary Tract ◽  
Human Body ◽  
Kidney Stone ◽  
Type Species ◽  
Phage Group ◽  
Content Type ◽  
Link Type ◽  
Abundance And Diversity ◽  
Cultured Bacteria

Bacteriophages (phages) are vital members of the human microbiota. They are abundant even within low biomass niches of the human body, including the lower urinary tract. While several prior studies have cultured bacteria from kidney stones, this is the first study to explore phages within the kidney stone microbiota. Here we report Dobby, a temperate phage isolated from a strain of Pseudomonas aeruginosa cultured from a kidney stone. Dobby is capable of lysing clinical P. aeruginosa strains within our collection from the urinary tract. Sequencing was performed producing a 37 152 bp genome that closely resembles the temperate P. aeruginosa phage φCTX, a member of the P2 phage group. Dobby does not, however, encode for the cytotoxin CTX. Dobby’s genome was queried against publicly available bacterial sequences identifying 44 other φCTX-like prophages. These prophages are integrated within the genomes of P. aeruginosa strains from a variety of environments, including strains isolated from urine samples and other niches of the human body. Phylogenetic analysis suggests that the temperate φCTX phage species is widespread. With the isolation of Dobby, we now have evidence that phages are members of the kidney stone microbiota. Further investigation, however, is needed to determine their abundance and diversity within these communities.

scholarly journals An antipathogenic compound that targets the OxyR peroxide sensor in Pseudomonas aeruginosa

2021 ◽  
Vol 70 (4) ◽  
Author(s):  
Hyo-Young Oh ◽  
Shivakumar S. Jalde ◽  
In-Young Chung ◽  
Yeon-Ji Yoo ◽  
Hye-Jeong Jang ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Drug Resistance ◽  
Stress Responses ◽  
Type Species ◽  
Reduced Form ◽  
Infection Model ◽  
Redox Cycle ◽  
Content Type ◽  
Link Type ◽  
Computer Based

Introduction. Antipathogenic or antivirulence strategy is to target a virulence pathway that is dispensable for growth, in the hope to mitigate the selection for drug resistance. Hypothesis/Gap Statment. Peroxide stress responses are one of the conserved virulence pathways in bacterial pathogens and thus good targets for antipathogenic strategy. Aim. This study aims to identify a new chemical compound that targets OxyR, the peroxide sensor required for the full virulence of the opportunistic human pathogen, Pseudomonas aeruginosa . Methodology. Computer-based virtual screening under consideration of the ‘eNTRy’ rules and molecular docking were conducted on the reduced form of the OxyR regulatory domain (RD). Selected hits were validated by their ability to phenocopy the oxyR null mutant and modulate the redox cycle of OxyR. Results. We first isolated three robust chemical hits that inhibit OxyR without affecting prototrophic growth or viability. One (compound 1) of those affected the redox cycle of OxyR in response to H2O2 treatment, in a way to impair its function. Compound 1 displayed selective antibacterial efficacy against P. aeruginosa in Drosophila infection model, without antibacterial activity against Staphylococcus aureus . Conclusion. These results suggest that compound 1 could be an antipathogenic hit inhibiting the P. aeruginosa OxyR. More importantly, our study provides an insight into the computer-based discovery of new-paradigm selective antibacterials to treat Gram-negative bacterial infections presumably with few concerns of drug resistance.

scholarly journals Study of quorum-sensing LasR and RhlR genes and their dependent virulence factors in Pseudomonas aeruginosa isolates from infected burn wounds

2021 ◽  
Vol 3 (3) ◽  
Author(s):  
Aya Ahmad Elnegery ◽  
Wafaa Kamel Mowafy ◽  
Tarek Ahmed Zahra ◽  
Noha Tharwat Abou El-Khier
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Proteolytic Activity ◽  
Virulence Factors ◽  
Biofilm Formation ◽  
Type Species ◽  
Assay Method ◽  
Content Type ◽  
Burn Wounds ◽  
Link Type

Background. Pseudomonas aeruginosa (P. aeruginosa) is an opportunistic pathogen responsible for burn-wound infection. High incidence, infection severity and increasing resistance characterize P. aeruginosa -induced burn infection. Purpose. To estimate quorum-sensing (QS)-dependent virulence factors of P. aeruginosa isolates from burn wounds and correlate it to the presence of QS genes. Methods. A cross-sectional descriptive study included 50 P . aeruginosa isolates from burn patients in Mansoura University Plastic and Burn Hospital, Egypt. Antibiotic sensitivity tests were done. All isolates were tested for their ability to produce biofilm using a micro-titration assay method. Protease, pyocyanin and rhamnolipid virulence factors were determined using skimmed milk agar, King’s A medium and CTAB agar test, respectively. The identity of QS lasR and rhlR genes was confirmed using PCR. Results. In total, 86 % of isolates had proteolytic activity. Production of pyocyanin pigment was manifested in 66 % of isolates. Altogether, 76 % of isolates were rhamnolipid producers. Biofilm formation was detected in 96 % of isolates. QS lasR and rhlR genes were harboured by nearly all isolates except three isolates were negative for both lasR and rhlR genes and two isolates were positive for lasR gene and negative for rhlR gene. Forty-nine isolates were considered as extremely QS-proficient strains as they produced QS-dependent virulence factors. In contrast, one isolate was a QS deficient strain. Conclusions. QS affects P. aeruginosa virulence-factor production and biofilm in burn wounds. Isolates containing lasR and rhlR seem to be a crucial regulator of virulence factors and biofilm formation in P. aeruginosa whereas the lasR gene positively regulates biofilm formation, proteolytic activity, pyocyanin production and rhamnolipid biosurfactant synthesis. The QS regulatory RhlR gene affects protease and rhamnolipid production positively.

scholarly journals Opinions 100, 101 and 102

2020 ◽  
Vol 70 (9) ◽  
pp. 5177-5181 ◽  
Author(s):  
David R. Arahal
Keyword(s):  
Type Strain ◽  
Type Species ◽  
International Committee ◽  
Type Material ◽  
Strain Atcc ◽  
Content Type ◽  
Nomenclatural Type ◽  
Link Type

The International Committee on Systematics of Prokaryotes has formally made final decisions, taking into account the conclusions of the Judicial Commission, on three pending Requests for an Opinion, thereby allowing the corresponding Opinions to be issued. According to Opinion 100, the request for the recognition of strain A1-86 (=DSM 17629=NCIMB 14373) as the neotype strain of Eubacterium rectale (Hauduroy et al. 1937) Prévot 1938 (Approved Lists 1980) is denied, ruling that a neotype does not need to be designated for E. rectale because strain VPI 0990 (=ATCC 33656=CIP 105953) is considered to be a duplicate isolate of the same strain as VPI 0989 (=ATCC 25578) and may serve as its nomenclatural type. Opinion 101 approves the request that strain ATCC 25946 (=DSM 14877) serves as the type strain of Melittangium lichenicola instead of strain ATCC 25944, formally correcting the Approved Lists of Bacterial Names. Opinion 102 concludes that strain Cc m8 (=DSM 14697=CIP 109128=JCM 12621) is an established neotype strain for the species Myxococcus macrosporus , replacing the designated type strain Windsor M271, and that strain Mx s8 (=DSM 14675=JCM 12634) is an established neotype strain for the species Myxococcus stipitatus , replacing the designated type strain Windsor M78, with some additional considerations about the nature of the type material replaced and about the name Corallococcus ( Myxococcus ) macrosporus.

scholarly journals Construction and evaluation of a bioluminescent Pseudomonas aeruginosa reporter for use in preservative efficacy testing

Microbiology ◽  
2021 ◽  
Vol 167 (8) ◽  
Author(s):  
Laura Rushton ◽  
Denise Donoghue ◽  
Matthew Bull ◽  
Peter Jay ◽  
Eshwar Mahenthiralingam
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Type Species ◽  
Random Mutagenesis ◽  
Light Output ◽  
Rapid Decline ◽  
Content Type ◽  
Link Type ◽  
Term Evaluation ◽  
Positive Attribute

Preservative efficacy testing (PET) is a fundamental practice in industrial microbiology used to ensure product shelf-life and quality. To improve on current growth-based PET, bioluminescence was evaluated as a real-time bacterial viability indicator using Pseudomonas aeruginosa . Random mutagenesis of an industrial P. aeruginosa strain with a promoter-less luxCDABE mini-Tn5 was used to select a stable reporter (LUX12H5) with an un-altered growth and preservative susceptibility phenotype. Bioluminescence and viability were measured with and without preservatives (isothiazolinones, phenoxyethanol, and dimethyl dimethylol hydantoin) and an antibiotic comparator (ciprofloxacin). In the absence of antimicrobials, a good correlation between bioluminescence and viability (r2=0.92) was established. However, metabolic inhibition by isothiazolinone preservatives caused a rapid decline in light output that did not correlate to a reduced viability. Conversely, after ciprofloxacin exposure, the decline in viability was greater than that of bioluminescence. A positive attribute of the bioluminescence was the early detection of metabolic recovery and re-growth of preservative injured bacteria. Overall, while initial bioluminescence read-outs were less suited to current PET requirements, it shows promise as an early, direct indicator of bacterial regrowth in the context of long-term evaluation of preservative efficacy.

Enterococcus saccharolyticus subsp. taiwanensis subsp. nov., isolated from broccoli

2013 ◽  
Vol 63 (Pt_12) ◽  
pp. 4691-4697 ◽  
Author(s):  
Yi-sheng Chen ◽  
Yu-hsuan Lin ◽  
Shwu-fen Pan ◽  
Si-hua Ji ◽  
Yu-chung Chang ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Dna Hybridization ◽  
Type Strain ◽  
Type Species ◽  
Phenotypic Traits ◽  
Strain Atcc ◽  
Content Type ◽  
Cellular Fatty Acids ◽  
Link Type ◽  
Emended Description

A coccal strain isolated from fresh broccoli was initially identified as Enterococcus saccharolyticus ; however, molecular identification and phenotypic traits did not support this identification. DNA–DNA hybridization with the type strain of E. saccharolyticus (76.4 % relatedness), DNA G+C content (35.7 mol%), phylogenetic analysis based on 16S rRNA, pheS and rpoA gene sequences, rep-PCR fingerprinting and profiles of cellular fatty acids, whole-cell proteins and enzyme activities, together with carbohydrate metabolism characteristics, indicated that this strain is distinct and represents a novel subspecies, for which the name Enterococcus saccharolyticus subsp. taiwanensis subsp. nov. is proposed. The type strain is 812T ( = NBRC 109476T = BCRC 80575T). Furthermore, we present an emended description of Enterococcus saccharolyticus and proposal of Enterococcus saccharolyticus subsp. saccharolyticus subsp. nov. (type strain ATCC 43076T = CCUG 27643T = CCUG 33311T = CIP 103246T = DSM 20726T = JCM 8734T = LMG 11427T = NBRC 100493T = NCIMB 702594T).

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